Godenir, Aurelien and Krier, Anthony (2008) Novel dilute nitride semiconductor materials for mid-infrared applications. PhD thesis, Lancaster University.
Abstract
A new approach to room temperature mid-infrared applications in the 3 -5 µm spectral range has been proposed through the development of novel dilute nitride materials. InAsN shows a large bandgap reduction with a small lattice mismatch when a small amount of nitrogen is introduced into the host InAs. Because the InAsN reported so far had generally poor crystalline quality and exhibited weak luminescence that quenched far below room temperature due to poorly understood localised states, the present thesis investigated the optimisation of the MBE growth of InAsN. The nitrogen incorporation was shown to be inversely dependent on the growth temperature, the growth rate and the arsenic flux, as was interpreted by a kinetic model. Luminescence from InAsN material showed two peaks, originating in bandgap-and localised state-related transitions. The emission related to the bandgap undergoes hardly any energy shift with increasing laser excitation power while it redshifts with increasing temperature. The emission from the localised states blueshifts with increasing laser excitation power and temperature. Rapid thermal annealing on InAsN layers improved the photoluminescence intensity and blueshifted the transition energy. InAsN was successfully grown with high crystalline quality. It showed strong photoluminescence which persisted up to room temperature with a reduced influence of the localised states and wavelength up to 4.5 µm was achieved when 2.5 % N were incorporated. An explanation of the temperature and nitrogen incorporation dependences of the InAsN bandgap was successfully proposed using Varshni's equation and an adapted band anticrossing model, where the nitrogen level energy is dependent on temperature and nitrogen composition. The crystalline quality and luminescence were both further improved by incorporating antimony into InAsN and strain balance in material for 4.2 µm applications was achieved with the novel InAsNSb alloy. A method to determine the composition of the quaternary was derived from bandgap models and lattice constant equation and the addition of antimony in InAsN was shown to enhance the nitrogen incorporation in InAsNSb. Finally, attempts at prototype InAsN and InAsNSb devices were reported, InAsNSb LEDs were demonstrated and electroluminescence from InAsNSb diodes at 3.88 µm at 4K was obtained.